It totally depends on the system layout, just as much as with mechanical suspension. Is it a trailing arm design, or a four point linkage with four bags ?
If it has a stabiliser bar, is it strong enough or could you swap it for a heavier one ? in lighter tow vehicles you need the optional heavy stabiliser to make it tow worthy, but a distribution truck like that FL 70 must have that as standard.
With a trailing arm airbag suspension the roll stability comes from the trailing arms which are bent during a roll. four point or three point linkage systems need a stabiliser bar (the U shaped thing) to provide roll stability.
In fact there are so many differences that you cant make a general rule of thumb between parabolic leaf or airbag suspension. (Since january i work at R&D for an air suspension manufacturer selling to OEMs from the USA to Australia, South Africa to asia, and there is a world of difference between what we compete against, you will find any type of system anywhere, but their popularity changes per region)
But as a general rule of thumb, modern day full air suspensions are layd out to provide better roll stability because with air suspension, you can get good roll stability without negative effects on the comfort with an empty vehicle.
If your truck has this double trailing arm design :
FAS II Airliner (Current Production) - Single/Tandem Axle Air Suspension Rear it will be fine
The only thing you might concider is swapping the shocks for aftermarket HD ones because of the sloshing septic. Driving half empty manure tanks behind a tractor is hardest to keep on the road, but you dont have that luxury, so improved shocks would help controlling the jerks.
If it has the older system, a crossover between air ride and leaf springs:
FAS Airliner (Past Production) - Single/Tandem Axle Air Suspension Rear i wont guarantee you it has the same roll stability as the newer air ride or the mechanical suspension... it looks peculiar to me, its a primitive crossover design, we stopped selling this style in 1982 in favour of a trailing arm design, for good reason... But its hard to judge from a picture so just try what it does.
